Abstract 14771: Chronotropic Incompetence and Response to Exercise Training by HIV Status in the Exercise for Healthy Aging Study

Abstract

Background: People with HIV (PWH) have lower exercise capacity compared to HIV-uninfected peers. Chronotropic incompetence (CI), the inability to increase heart rate during exercise, may contribute to reduced exercise capacity. We hypothesized that PWH would have lower adjusted heart rate reserve (AHRR=(HR peak -HR rest )/(220-Age-HR rest ), a measure of chronotropy, normal >80%) and that AHRR would improve with exercise training. Methods: The Exercise for Healthy Aging Study included sedentary adults ages 50-75 with (PWH) and without HIV (controls) recruited for a 24-week exercise training program. Participants exercised at moderate intensity for weeks 1-12 and were then randomized to continue moderate or advance to a higher intensity of exercise for weeks 13-24. We compared prevalent CI on treadmill cardiopulmonary exercise testing by HIV. We compared AHRR and change in AHRR from baseline to 12 and 24 weeks by HIV status using mixed effects models. Finally we explored whether improved chronotropy could explain the greater benefit of exercise observed among PWH. Results: Among 32 PWH and 37 controls (median age 56, 7% female, mean BMI 28 mg/m 2 ), 9/31 (29%) with HIV compared to 4/38 (11%) controls had CI (p=0.07). At entry, AHRR was lower among PWH (91 vs 102%; difference 11%, 95%CI 2.5-19.7; p=0.01). At week 12, AHRR normalized among 27 PWH (+8%, 95%CI 4-11; p<0.001) and sustained at week 24 (+5, 95%CI 1-9; p=0.008) compared to no change among 31 controls (95%CI -4 to 4; p=0.95; p interaction =0.004). Accounting for AHRR, the greater benefit of exercise observed among PWH at 12 weeks (peak VO 2 +1.5 ml/kg/min more than controls, 95%CI 0.1 to 2.9, p=0.04) was attenuated (0.4 ml/kg/min independent of AHRR, 95%CI -0.9 to 1.8; p=0.53). After 24 weeks of exercise, only 4/26 (15%) PWH met the definition for CI compared to 3/29 (10%) of controls (p=0.70). Conclusions: Chronotropic incompetence may contribute to reduced exercise capacity among PWH and improve with exercise training.